Space, number, and time provide fundamental sources of information by which we (and other animals) structure experience in the world. Although these dimensions can be processed independently, there are well- documented associations between each pair: space and number (e.g., Dehaene, Bossini, &Giraux, 1993), space and time (e.g., DeLong, 1981), and number and time (e.g., Meck &Church, 1983). The pervasive nature of these associations has led to the suggestion that all three dimensions form part of a system of general magnitude representation, perhaps with common processing mechanisms in overlapping brain regions (e.g., Walsh, 2003). Recent speculation has concerned the possibility that general magnitude representation occurs early in human life (e.g., Feigenson, 2007). In a world where space, number, and time are highly correlated, representing magnitude information more generally might well be advantageous, perhaps allowing for greater efficiency of processing. The advantages, however, would not guarantee early developmental beginnings. The goal of the proposed research is to examine general magnitude representation in human infants. Do associations among space, number, and time exist in infancy, prior to long-term interactions with statistical regularities in the physical world and to linguistic experiences that may highlight associations? The existing empirical evidence is limited;no study with preverbal infants has tested directly whether magnitude is represented more generally across different dimensions. In the proposed research, we develop a task suitable for examining general magnitude representation in infancy. We begin by using this task to examine how infants represent ordinal relations for size, numerosity, and duration. In Exp. 1, we test the extent to which 9-month- olds can learn arbitrary color/pattern mappings for each dimension;for example infants might be taught that sets of bigger-sized objects are always black with white stripes and smaller-sized objects are always white with black dots. We then build on this experiment by testing directly the associations among size, numerosity, and duration. In Exp. 2, we examine whether 9-month-olds'learning related to one dimension of magnitude transfers to other magnitude dimensions;for example, do infants later expect larger-numerosity arrays to exhibit the black/stripes property and smaller-numerosity arrays to exhibit the white/dots property? A system of general magnitude representation could allow for transfer across space, number, and time. By testing preverbal infants and comparing associations among all three dimensions, this research is expected to make a unique contribution to theories concerning the nature and early functioning of general magnitude representation. The proposed studies are important for shedding light on how the young mind organizes core dimensions of experience, and they form part of my larger research program, which aims to enhance our understanding of the psychological, neural, and adaptive underpinnings of general magnitude representation. PUBLIC HEALTH RELEVANCE: A basic understanding of early cognitive abilities is essential in a wide variety of clinical and educational contexts, and it is interesting to parents and the society at large. The proposed research is concerned with how the young mind organizes core dimensions of experience: space, number, and time. The ability to represent magnitude-related information is among the most fundamental of cognitive capacities, and this ability may predict a variety of later health and educational outcomes.